1
JI Ve311 Homework #3
Note:
(1) Please use A4 size papers.
(2) Please use the SPICE model below for simulation.
.model Qbreakn NPN IS=4e-16 BF=100 VAF=50
1. [BJT Forward-Active I-V Characteristics] For a npn BJT circuit as below:
(a) [20%] When VBE = 0.7 V and VCE = 2 V , use proper equations
provided in the course slides and the spice model above to calculate
the gm and ro.
(b) [10%] In Pspice, when VCE = 2 V, plot IC versus VBE (increasing
from 0 to 1 V). Find out the slope at VBE = 0.7 V and compare it with
the gm value calculated in (a).
(c) [10%] In Pspice, when VBE = 0.7 V, plot IC versus VCE (increasing
from 1 to 3 V). Find out the inverse of the slope at VCE = 2 V and
compare it with the ro value calculated in (a).
2
2. [BJT Common-Emitter Amplifier] For a npn BJT circuit as below:
(a) [30%] When VIN = 0.7 V , use proper equations provided in the
course slides and the spice model above to calculate the small-signal
voltage gain (Aυ =
υout
υin
). Hint: take Early Effect into consideration.
(b) [15%, DC Sweep] In Pspice, plot VOUT versus VIN (increasing from 0
to 1 V). Find out the slope at VIN = 0.7 V and compare it with the
voltage gain calculated in (a).
(c) [15%, Transient Analysis] In Pspice, when Vin = 0.7 + 0.001 ∙
sin(2π100 ∙ time) V, plot Vout and Vin versus time (from 0 to 0.1
second). Find out |Aυ
| = |
υout
υin
| and compare it with the voltage gain
calculated in (a).
